Coupler lock



FIG. 1 is a perspective view of a coupler lock showing my new design;

FIG. 2 is a top plan view thereof;

FIG. 3 is a bottom plan view thereof;

FIG. 4 is a right side view thereof;

FIG. 5 is a left side view thereof;

FIG. 6 is a front plan view thereof; and,

FIG. 7 is a rear plan view thereof. 

The ornamental design for a coupler lock, as shown and described. 